Modify course command words

[accountexeregister]

closes #121

Changes the following course commands:

• course -> course-add
• edit-course -> course-edit
• delete-course -> course-delete

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 74.07407% with 7 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...tacts/logic/commands/course/CourseEditCommand.java	66.66%	0 Missing and 2 partials :warning:
...s/logic/parser/course/CourseEditCommandParser.java	50.00%	1 Missing and 1 partial :warning:
...tahub/contacts/logic/parser/AddressBookParser.java	66.66%	1 Missing :warning:
...ts/logic/parser/course/CourseAddCommandParser.java	66.66%	0 Missing and 1 partial :warning:
...logic/parser/course/CourseDeleteCommandParser.java	66.66%	0 Missing and 1 partial :warning:

Files with missing lines	Coverage Δ	Complexity Δ
...ntacts/logic/commands/course/CourseAddCommand.java	100.00% <100.00%> (ø)	7.00 <1.00> (?)
...cts/logic/commands/course/CourseDeleteCommand.java	100.00% <100.00%> (ø)	8.00 <1.00> (?)
...tahub/contacts/logic/parser/AddressBookParser.java	75.00% <66.66%> (ø)	14.00 <0.00> (ø)
...ts/logic/parser/course/CourseAddCommandParser.java	66.66% <66.66%> (ø)	4.00 <1.00> (?)
...logic/parser/course/CourseDeleteCommandParser.java	72.72% <66.66%> (ø)	4.00 <1.00> (?)
...tacts/logic/commands/course/CourseEditCommand.java	79.16% <66.66%> (ø)	9.00 <2.00> (?)
...s/logic/parser/course/CourseEditCommandParser.java	62.50% <50.00%> (ø)	4.00 <1.00> (?)